>>1170981A tram can still use a public road but with a tram only lane therefore not all trams get caught in traffic. Also, a tram can have traffic light priority, where it turns up at the lights and the signal makes everything else on the road give way to the tram.
Also, the fact that they travel a set route is not really a disadvantage, because it's a reassurance of where you're going, and moreover metropolitan area routes where trams would operate do not change often. And really, one could even argue this could extend to cargo trams. If one had tram tracks down alleys, the trams could be used to service inner metropolitan buildings with delivery services. Those buildings are hardly going away in the city core.
>>1170868While it may be impractical in existing cities, a city with a planned tram network could easily plan for tram-serviced alleys. The vehicles wouldn't be any wider than delivery trucks, and if planned properly they would even have a good turning radius back onto the streets proper.